A virtual technique for servers or networks is utilized in a network system for flexible configuration and easy management. With use of the virtual technique, resources such as servers or networks can be utilized without depending on the physical configuration. This is because the physical configuration is hidden against the higher orders in the visual technique, thereby freely using resources.
There is provided a technique which applies a switch network virtual technique for constructing a multi-tenant compatible cloud data center thereby to provide resources without any restriction on a server rack housing position also when a plurality of tenant users are to be housed (see NPL 1, for example).